1. Field of the Invention
The present invention relates to an image forming apparatus and method therefor, in which a processing apparatus such as a personal computer, and a printing/stencil making apparatus such as a printer, a word processor, a processing machine and the like are used to directly form a desired image on a color image forming sheet having a color area of a plurality of colors formed in advance regularly, or to perform heat-sensitive perforation by a desired image on a screen base paper to form an image on a color image forming sheet by a screen press using the screen base paper subjected to heat-sensitive processing.
2. Description of the Related Art
For the purpose of obtaining a desired color image by a handy means, the present applicant has proposed a color image forming sheet having a color area regularly constituted by a plurality of colors (Japanese Patent Laid-Open No. 137349/1995).
The color image forming sheet is a sheet in which inks of three primary colors comprising cyan (C), magenta (M) and yellow (Y) are printed in a predetermined type on a sheet-like substrate such as paper.
As the predetermined type of the color image forming sheet 11, there is employed a stripe pattern in which color inks are printed in the constant order alternately without clearance so as to form stripes each having a predetermined width, as shown in an enlarged view of FIG. 11. With this, the color image forming sheet 11 appears to be the ground color of a gray base such as black or gray as a whole by a mixture of colors. Alternatively, the color image forming sheet 11 with the ground color such as a cream base, a green base, a pink base and the like as a whole is obtained by combining colors different in reflecting concentration in the color areas.
When the printing width of each stripe is, for example, 0.1 to 0.22 mm, each color is repeated with a pitch of 0.3 to 0.66 mm.
If, for example, white ink is placed on a part of the color image forming sheet 11 for printing, ink in a portion remaining without being covered is mixed in color to form a constant color. For example, as shown in FIG. 12, if only a portion of yellow Y of the color image forming sheet 11 is concealed by white ink in a web-like manner, the color image forming sheet 11 appears to be blue (or purple) as a whole by a mixture of remaining cyan C and magenta M.
Further, as shown in FIG. 13, if white ink is printed in a web-like manner on a part of yellow Y and the whole cyan C of the color image forming sheet 11, the color image forming sheet 11 appears to be red as a whole by a mixture of a part of yellow Y and magenta M remained.
As described above, a part of the color image forming sheet 11 is covered with a predetermined pattern by changing a line width and a spacing of the pattern according to the line width and the spacing of color areas in the color image forming sheet 11 whereby a desired color image can be represented by a mixture of the ground colors not concealed.
A predetermined pattern covering a part of the color image forming sheet 11 is formed in a stencil sheet by heat-sensitive boring, and a desired color image is formed on the color image forming sheet 11 using the stencil sheet thus heat-sensitively perforated. Then, a desired color can be displayed on the color image forming sheet 11 as described above. In the case where a color is displayed on the color image forming sheet by printing using a perforated stencil sheet, as described above, the processing procedure generally contemplated will be described below.
For this treatment, there is used a film-like transparent sheet formed on the whole surface thereof with white stripes having a predetermined line width and spacing. The transparent sheet is set in the line width and spacing of the stripes according to which a part of color areas of the color image forming sheet is covered. Plural kinds of transparent sheets different in the line width and spacing are prepared.
First, a suitable sheet is selected out of the plural kinds of transparent sheets according to the line width and spacing of the stripes of the color image forming sheet on which an image is printed. This single transparent sheet is placed over the whole surface of a sheet on which an original image is depicted and copied by a copier. The obtained copy is a stripe-like image in which a portion on which white color of the transparent sheet is in the form of white. Next, only a necessary figure is cut out of the copied sheet, which is edited by a combination thereof with other figures if necessary and affixed to a suitable sheet to copy it again, thus obtaining an original. A stencil sheet is perforated by the heat-sensitive perforation using the aforesaid original. By using the thus perforated stencil sheet, printing is carried out relative to the color image forming sheet by the printing/stencil making apparatus.
In addition to the aforementioned processing, the following method may be contemplated. An original on which the original image itself is formed in advance in a stripe-like form is prepared. The heat-sensitive perforation is applied to a stencil sheet by the aforesaid original, and printing is carried out relative to the color image forming sheet using the thus perforated stencil sheet.
If the perforated stencil sheet obtained as described above is used, ink transferred from the perforated portion of the stencil sheet covers a part of a color area of the color image forming sheet. A desired color image is formed on the color image forming sheet by a mixture of colors not concealing the color area.
However, in the aforementioned method, it is necessary to prepare plural kinds of transparent sheets on which stripes different in the line width and spacing for forming an image on a stencil sheet and to take a copy using the transparent sheet selected therefrom. This poses a problem in that many materials such as transparent sheets and sheets for copying are consumed. Moreover, since most of work are manually done, the work itself was cumbersome. In addition, in the method of using an original in which the original image itself is formed in advance in a stripe-like form, a color pattern depicted on the color image forming sheet tends to be fixed, thus making it difficult to expand the width of an expressive power.